1. Technical Field
The present invention relates to an antenna device capable of achieving reduction in size and an electronic timepiece including the antenna device.
2. Related Art
In the related art, for an antenna device which can be provided in an electronic timepiece, a configuration in which an antenna is provided to be bonded to a display plate (character plate) of an electronic timepiece is disclosed. With this configuration, the antenna is provided on the rear side of the display plate, that is, on a non-visible side, thereby avoiding the design appearance of the electronic timepiece from being damaged due to the antenna. The electronic timepiece can have a noncontact data communication function while substantially maintaining the appearance in the related art (see JP-A-2003-66169).
As an example, an antenna device is known which has a plurality of (two) chip-like elements. With this antenna device, it is possible to receive circularly polarized waves, such as GPS (Global Positioning System) electric waves. The elements of the antenna device can be used as dials of a character plate for an electronic timepiece. The antenna device can have a function as a part of design elements of the electronic timepiece, in addition to a function as an antenna (for example, JP-A-2007-124011).
In the related art, these antenna devices are provided in electronic timepieces in which the antenna devices are difficult to be mounted due to the restriction of design, size, and the like. This contributes to the functional extension of an analog electronic timepiece.
As another example, a receiver (antenna device) in an electronic timepiece in which a planar receiving antenna functioning as an electric wave receiving terminal and a timepiece unit having a digital display unit are arranged in an overlapping manner. In the example of the receiver, while the planar receiving antenna and the timepiece unit do not simply overlap each other, a cover glass of the timepiece unit is used as an antenna dielectric of the planar receiving antenna, and a conductive thin film is provided in the cover glass. With this configuration, it becomes possible to achieve a reduction in the size of the receiver (for example, JP-A-10-197662).
However, according to the technique of JP-A-2003-66169, in order to increase communication sensitivity, there is the restriction that a material for a region of the display plate where the antenna is attached should be an insulating member, not a conductive member, and there is a problem from the viewpoint of selection of the material of the display plate, surface treatment relating to design, or the like. According to the technique of JP-A-2007-124011, there are problems in that a plurality of elements should be arranged such that the reception characteristic directions cross each other, it is necessary to provide phase changing means for changing the phase of a received signal so as to show a phase difference based on the crossing angle of the reception characteristic directions, and complicated control should be performed. According to the technique of JP-A-10-197662, since the cover glass is used as the antenna dielectric, feed terminals for feeding power to a conductive thin film and the conductive thin film are provided on the front surface of the cover glass, that is, on the side where the time is visible, and there is the restriction that it is necessary to take into consideration the arrangement such that visual recognition of the time or the like is not obstructed, friction resistance, corrosion resistance, and the like.